Winchester NATO-Spec Armed forces Primers forty one are the identical primers used in the Lake Metropolis five.56mm ammunition. These primers are created to exacting specifications for shot to shot regularity. All primers are continuously and rigorously examined for regularity and sensitivity at temperatures and situations considerably over and above the selection of usual usage. Winchester guarantees thoroughly-managed weights of primer mixtures, consistency in measurement and high-quality, precise measurements and tolerances for anvil heights and balance in extremes winchester 41 primers of temperatures and humidity.